Recording material for electrostatic or electrographic recordings

ABSTRACT

Electrostatic or electrographic recording material comprising a microporous synthetic thermoplastic polymer as a sheet-like base material, having a content of at least 20 wt %, based on the total weight of the base material, of finely dispersed inorganic fillers and comprising an electrically conductive layer arranged on at least one surface of said base material, and a dielectric recording layer disposed on the electrically conductive layer.

The invention relates to a multilayer recording material forelectrostatic or electrographic recordings.

PRIOR ART

Such recording materials are known in principle. They often comprise apolymer base layer having suitable dimensional stability, which has anelectrically conductive layer on at least one surface and further has adielectric recording layer disposed on the electrically conductivelayer.

However, conventional recording materials of this type do not, whencolored areas are produced, meet the necessary requirements in terms ofimage quality, adhesion of the pigment material or the toner on therecording layer to allow solid-colour recordings to be produced in artquality.

SUMMARY OF THE INVENTION

The object of the present invention is to improve the known recordingmaterials.

This object is achieved by a multilayer electrostatic or electrographicrecording material comprising a polymer base material and anelectrically conductive layer disposed on at least one surface of thebase material, and a dielectric recording layer disposed on theelectrically conductive layer, wherein, the polymer base material is amicroporous synthetic thermoplastic polymer having a content of at least20 wt %, based on the total weight of base material, of finely dispersedinorganic fillers.

DETAILED DESCRIPTION OF THE INVENTION

The sheet-like base material to be used preferably comprises apercentage of filler of at least 40 wt %, based on the total weight ofthe support material. The percentage of filler can be up to 90 wt %, butis preferably in the range of 30-80 wt %.

Suitable as finely dispersed inorganic fillers are calcium carbonate,kaolin, aluminum oxide, aluminum hydroxide, barium sulfate, precipitatedsynthetic silica or fumed silica or mixtures thereof.

Prior to being incorporated into the polymer material the filler mayhave an average particle size of from 0.01 to 40 μm, preferably of from0.1 to 25 μm, particularly preferably of from 0.1 to 3 μm.

The filler may also be present in the form of aggregated primaryparticles or agglomerates thereof, although these may undergo sizereduction when being introduced into the polymer material. In thepolymer matrix the filler is therefore often present in a more finelydispersed form than prior to its introduction.

The thermoplastic polymer for the base material may comprisepolyolefins, in particular polypropylene or polyethylene, polyester,polystyrene, polyamide or poly(vinyl chloride).

Especially preferred are linear polyolefins having a very high molecularweight, for example essentially linear polyethylene or isotacticpolypropylene, the molecular weight being very high in each case. Themolecular weight can be determined via the intrinsic viscosity inaccordance with ASTM D 4020-81. In the case of the polyolefins theviscosity should be from 18 to 40 dl/g.

The high percentage of filler in the polymer matrix means that the basematerial overall is microporous. The volume fraction of theinterconnected pores is more than 50 vol %, preferably more than 80 vol%, and may attain up to 95 vol %. This can be achieved by the material,having been drawn into a film after the fillers have been incorporatedinto softened polymer, is additionally extracted with solvents whichwill not dissolve the polymer or cause it to swell, to extractprocessing aids such as plasticisers.

The base material has a microporous structure in which the filler isembedded in a matrix of synthetic polymers. This structure produces awater absorption capacity, determined by means of the Cobb value inaccordance with ISO 535-1976(E) with a measuring time of 12 seconds, offrom 30 g/m² to 120 g/m², preferably at least 50 g/m².

Advantages also attach to biaxial stretching and optionally thermalafter-treatment of the highly filled polymer film prior to theapplication of the electrically conductive layer onto at least one ofthe surfaces of the microporous base material.

The microporous structure and the good water absorption capacity of thebase material cause the electrically conductive polymers, which areapplied from an aqueous medium to form the electrically conductivelayer, to penetrate deeply into the base material and not only to reducethe surface resistivity of the base material provided with theelectrically conductive layer to values of from 1×10⁵ to 1×10¹³,preferably from 1×10⁶ to 1×10⁹ ohms per square at 20° C. and 50%relative humidity, but also reduce the volume resistance of the coatedbase material. Prior to the application of the electrically conductivepolymer onto the microporous base material the electrical volumeresistance is 1.5×10 ohms×cm. After the application of the electricallyconductive polymers the electrical volume resistance is 6×10⁶ ohms×cm to10×10⁹ ohms×cm.

Electrically conductive polymers suitable for coating and impregnatingthe porous base material include sulfonated polystyrenes, copolymers ofdimethylammonium chloride and diacetone acrylamide,poly(dimethyldialkylammonium), quaternary cellulose acetates, quaternaryacrylic resins, poly(vinyl butyral) derivatives, copolymers ofdimethyldiallylammonium chloride and N-methylacrylamide, and otherpolymers known to form electrically conductive layers.

The electrically conductive polymer or polymer mixture is applied ontoand into the microporous base material in an amount of from 0.5 to 5g/m², preferably from 1 to 3 g/m², to ensure that the electrical surfaceand volume conductivity of the base material is adequate for dielectricrecording materials.

The electrical conductivity of the base material after application ofthe polymers is humidity-independent over a wide range of from 10%relative ambient humidity to 85% relative ambient humidity.

Present on the electrically conductive layer is a dielectric recordinglayer having a surface resistivity of from 0.3×10⁶ to 3×10⁹ ohms/square,so that applied static electric charge persists for a sufficiently longtime in the form of a latent image to allow conventional toner materialto be deposited on the recording layer to generate an image.

Suitable for forming the dielectric layer are, in particular,film-forming polymers which also serve as binders for fillers and/orpigments and which confer upon the layer an electrical volume resistanceof 10¹² ohms×cm or more.

The layer may have a thickness of from 2 to 10 μm, the coating weightmay be 1-5 g/m².

Examples of suitable polymers are polystyrene, polycarbonates,polyolefins (which may or may not be halogenated) such as polyethylene,polypropylene, polybutylene, (meth)acrylic resins, poly(vinyl butyral),polyester resins, polyvinyl resins, cellulose acetates, epoxy resins.Mixtures of compatible polymers can also be used.

Examples of pigments/fillers present in the dielectric layer are finelydispersed fumed silica, calcium carbonate, aluminum silicate and/orfinely dispersed organic pigments.

The percentage of pigments may be from 4 wt % to 55 wt %, based on thetotal weight of the dielectric layer.

The coating composition may further contain conventional aids such asdispersants, wetting agents, anti-foaming agents, UV stabilizers, if thedielectric behavior of the layer formed after drying of the aqueouscoating composition applied is not impaired thereby.

The invention will now be explained in more detail with reference to thefollowing examples.

EXAMPLE 1

The microporous polymer base material used is a commercially availablemicroporous filled film on a polyolefin basis (polyethylene basis,manufacturer PPG IND. INC., Pittsburgh, Pa.).

To form the electrically conductive layer, an aqueous compositioncomprising 40 parts by weight of methanol, 47 parts by weight of waterand 13 parts by weight of a water-soluble polycationic polymer (EMISTAD6300H from Sanjo Chemical Industries) is employed.

After drying the coated/impregnated microporous base material contains1.2 g/m² of conductive polymer. The electrical surface resistivity at50% relative humidity and 20° C. is 1×10⁷ ohms/square on one side and1.5×10⁷ ohms/square on the opposite surface. The electrical volumeresistance is 3.5×10⁶ ohms×cm and 4×10⁶ ohms×cm, respectively.

To form the dielectric recording layer, the following coatingcomposition is employed:

    ______________________________________                                        Toluene                 71.3 parts by weight                                    Isopropanol 11.5 parts by weight                                              Poly (vinyl butyral) (B 76, Monsanto Chemical Co.)  8.6 parts by weight       (Molecular weight 34,000-38,000)                                              Natural calcium carbonate  7.6 parts by weight                                (Calcilit 4, Grace)                                                           Amorphous silicon dioxide  0.5 parts by weight                                (Syloid Al 1, Grace)                                                          Synthetic amorphous silica  0.5 parts by weight                               (OK 412, Degussa)                                                           ______________________________________                                    

A dielectric layer having an areal density of 2 g/m² is formed.

The specific electrical surface resistivity of the dielectric layer is1×10⁸ ohms/m², the electrical volume conductivity of the recordingmaterial is 5×10⁷ ohms×cm.

EXAMPLE 2

The microporous polymer base material used is a commercially availablefilled film on a polyolefin basis (polyethylene basis, manufacturer PPGIND. INC.).

To form the electrically conductive layer, the microporous base materialis coated with the following composition:

    ______________________________________                                        Methanol              20 parts by weight                                        Water 67 parts by weight                                                      Quaternary polymeric compound  9 parts by weight                              (Makrovil ECR 69L, Indulor GmbH)                                              Poly (vinyl alcohol)  4 parts by weight                                       (Mowiol 4/88, Hoechst)                                                      ______________________________________                                    

After drying, the microporous base material contains about 2.5 g/m² ofthe solids of the coating composition.

The electrical surface resistivity at 50% RH and 20° C. is 1.5×10⁷ohms/square on one side and 3×10⁷ ohms/square on the opposite side. Theelectrical volume resistance is 7×10⁶ ohms×cm.

To form the dielectric recording layer a coating composition is usedwhich comprises:

    ______________________________________                                        Toluene                  68 parts by weight                                     Isopropanol  16 parts by weight                                               Poly (vinyl butyral)   9 parts by weight                                      (Butvar B-76, from Monsanto Chemical Co.)                                     Natural calcium carbonate   6 parts by weight                                 Amorphous silicon dioxide 0.5 parts by weight                                 Synthetic amorphous silica 0.5 parts by weight                              ______________________________________                                    

The coating weight of the dielectric layer is 2 g/m² of the dryconstituents of the coating composition.

The specific electrical surface resistivity of the dielectric recordinglayer is 1×10⁸ ohms/square. The electrical volume conductivity is 3×10⁷ohms×cm.

EXAMPLE 3

Use is made of the microporous base material coated with an electricallyconductive polymer according to Example 1.

To form the dielectric layer, a coating composition is applied whichcomprises:

    ______________________________________                                        Toluene                  74 parts by weight                                     Isopropanol  14 parts by weight                                               Poly (vinyl butyral) 7.0 parts by weight                                      (Butvar B-76, from Monsanto Chemical Co.)                                     Calcium carbonate (Calcilit 4) 4.4 parts by weight                            Amorphous silicon dioxide 0.2 parts by weight                                 (Syloid Al 1, Grace)                                                          Synthetic amorphous silica 0.4 parts by weight                                (OK 412, Degussa)                                                           ______________________________________                                    

The dielectric layer is applied in an amount of 2 g/m² of the dryconstituents of the coating composition. The dielectric recording layerhas an electrical surface resistivity of 3×10⁷ ohms/square and anelectrical volume resistance of 2.5×10⁷ ohms×cm at 50% RH and 20° C.

EXAMPLE 4

For this example use is made of the microporous base material, madeelectrically conductive, of Example 2.

To form the dielectric recording layer a coating composition is usedwhich comprises:

    ______________________________________                                        Toluene              25 parts by weight                                         Acetone 56 parts by weight                                                    Amorphous sodium/aluminum  3 parts by weight                                  silicate (P 820, Degussa)                                                     Poly (vinyl acetate)/crotonic 16 parts by weight                              acid copolymer (Mowilit CT 5                                                  from Hoechst)                                                               ______________________________________                                    

The coating weight of the dielectric layer is 4 g/m².

The dielectric recording layer has a specific surface resistivity of1.5×10⁷ ohms/square on the one side and 3×10⁷ ohms/square on theopposite side.

EXAMPLE 5

A microporous base material according to Example 2 is coated, to formthe electrically conductive layer, with a composition comprising:

    ______________________________________                                        Isopropanol         1.0 part by weight                                          Water  90 parts by weight                                                     Poly (vinyl alcohol) 9.0 parts by weight                                    ______________________________________                                    

After drying the microporous base material contains 2 g/m² of the dryconstituents of the coating composition.

The electrical surface resistivity at 50% RH and 20° C. is 3×10⁹ohms/square, and the electrical volume resistance is 2×10⁷ ohms/cm.

The dielectric layer is formed, with an areal density of 5 g/m², fromthe following composition:

    ______________________________________                                        Toluene              54.5 parts by weight                                       Vinyl copolymer (Synocryl 28.3 parts by weight                                877 S from Cray Valley Prod.)                                                 Amorphous silica coated 0.85 parts by weight                                  with fluoride (Silcron G 300                                                  from Langer & Co. GmbH)                                                       Amorphous silicon dioxide 0.85 parts by weight                                (Syloid Al 1, Grace)                                                          Calcium carbonate 17.5 parts by weight                                        (Calcidor 5, Omya)                                                          ______________________________________                                    

The electrical surface resistivity of the recording layer is 7×10¹¹ohms/square, and the electrical volume resistance is 1×10¹⁰ ohms/cm.

EXAMPLE 6

A microporous base material according to Example 2 was equipped with anelectrically conductive layer by a composition being applied whichcomprised:

    ______________________________________                                        Methanol             62 parts by weight                                         Glycol  7 parts by weight                                                     Water soluble polycationic 31 parts by weight                                 polymer (Chemistat 6300 H                                                     Sanjo Chemical Industries)                                                  ______________________________________                                    

After drying, the microporous base material contains 1.5 g/m² of the dryconstituents of the coating composition.

The electrical surface resistivity is 2.5×10⁶ ohms/square on one sideand 3.5×10⁶ ohms/m² on the opposite side. The electrical volumeresistance is 3×10⁶ ohms×cm, each measured at 50% RH and 20° C.

The dielectric recording layer is formed from a coating compositioncomprising:

    ______________________________________                                        Toluene               62 parts by weight                                        Vinyl copolymer (Synocryl  37 parts by weight                                 877 S from Cray Valley Prod.)                                                 Synthetic amorphous silica 0.5 parts by weight                                (OK 412, Degussa)                                                             Synthetic amorphous silica 0.5 parts by weight                                (FK 320, Degussa)                                                           ______________________________________                                    

The dielectric layer has an areal density of 6 g/m² and an electricalsurface resistivity of 2.5×10⁷ ohms/square at 50% RH and 20° C. Theelectrical volume resistance of the recording material is 1.5×10⁷ohms×cm.

EXAMPLE 7

This example makes use of the microporous base material, equipped withan electrically conductive layer, of Example 1.

To form the dielectric layer, a coating composition is applied with anareal density of 6 g/m², comprising:

    ______________________________________                                        Toluene              60 parts by weight                                         Vinyl copolymer (Synocryl 38 parts by weight                                  877 S from Cray Valley Prod.)                                                 Synthetic amorphous silica  2 parts by weight                                 (OK 412, Degussa)                                                           ______________________________________                                    

The electrical surface resistivity of the dielectric recording layer is6×10⁷ ohms/square, and the recording material has an electrical volumeresistance of 2×10⁷ ohms×cm, each measured at 50% RH and 20° C.

EXAMPLE 8

Applied onto a microporous base material (filled polyolefin film), toform an electrically conductive layer, is a coating composition whichcomprises:

    ______________________________________                                        Water                 70 parts by weight                                        Poly (vinyl alcohol)  3 parts by weight                                       (4/98, Hoechst)                                                               Water soluble polycationic 24 parts by weight                                 polymer (Chemistat 6300 H from                                                Sanjo Chemical Industries)                                                    Synthetic amorphous silicic  3 parts by weight                                acid (OK 412, Degussa)                                                      ______________________________________                                    

The amount applied, as dry matter, is 0.8 g/m².

The synthetic microporous base material rendered electrically conductivehas an electrical surface resistivity of 3.5×10⁶ ohms/square and anelectrical volume resistance of 3×10⁶ ohms×cm, each measured at 50% RHand 20° C.

Applied onto this base material, to form the dielectric recording layer,is a composition which comprises:

    ______________________________________                                        Toluene               63 parts by weight                                        Vinyl copolymer  28 parts by weight                                           Synthetic amorphous silicic 0.8 parts by weight                               acid (OK 412, Degussa)                                                        Amorphous silicon dioxide 0.8 parts by weight                                 (Syloid Al 1, Grace)                                                          Calcium stearate 7.4 parts by weight                                        ______________________________________                                    

The coating weight is 5 g/m².

The dielectric recording layer, at 50% RH and 20° C., has an electricalsurface resistivity of 3×10⁷ ohms/square and an electrical volumeresistance of 6×10⁶ ohms×cm

EXAMPLE 9

Preparation of a porous polymer substrate comprising polypropylene.

    ______________________________________                                        Paraffin oil (Merck,                                                                             3800 g                                                       Darmstadt, #10 06 71)                                                         Silica (FK 310, Degussa) 620 g                                                Stearic acid (Merck, 12 g                                                     Darmstadt, #10 06 71)                                                         Antioxidant (Irganox D215, 15 g                                               Ciba-Geigy)                                                                   Polypropylene powder 470 g                                                    (#18 239-7, Aldrich)                                                        ______________________________________                                    

The paraffin oil is heated to about 105° C. and the silica, the stearicacid and the antioxidant are dispersed therein by 10 minutes' stirring.Then the polypropylene powder is incorporated by 10 minutes' stirring.The mixture is molded into a sheet through a slot die having a gap widthof 200 μm. The sheet obtained is treated by means of a calender and inthe process cooled to room temperature. The paraffin oil is thenextracted with trichloroethylene. After drying the porous sheet has awater absorption capacity, according to Cobb, of 80 g/m².

To form the electronically conductive layer, the microporous basematerial is coated with the following composition:

    ______________________________________                                        Methanol              20 parts by weight                                        Water 67 parts by weight                                                      Quaternary polymeric compound  9 parts by weight                              (Makrovil ECR 69L, Indulor GmbH)                                              Poly (vinyl alcohol)  4 parts by weight                                       (Mowiol 4/88, Hoechst)                                                      ______________________________________                                    

After drying, the microporous base material contains about 2.5 g/m² ofthe solids of the coating composition.

The electrical surface resistivity at 50% RH and 20° C. is 2.0×10⁷ohms/square on one side and 3.2×10⁷ ohms/square on the opposite side.The electrical volume resistance is 7.2×10⁶ ohms×cm.

To form the dielectric recording layer a composition is used, whichcomprises:

    ______________________________________                                        Toluene                  68 parts by weight                                     Isopropanol  16 parts by weight                                               Poly (vinyl butyral)   9 parts by weight                                      (Butvar B-76, from Monsanto Chemical Co.)                                     Natural calcium carbonate (Calcilit 4)   6 parts by weight                    Amorphous silicon dioxide 0.5 parts by weight                                 (Syloid Al 4, Grace)                                                          Synthetic amorphous silicic 0.5 parts by weight                               acid (OK 412, Degussa)                                                      ______________________________________                                    

The coating weight of the dielectric layer is 2 g/m² of the dryconstituents of the coating composition.

The electrical surface resistivity of the dielectric recording layer is1.5×10⁸ ohms/square. The electrical volume resistance is 3×10⁷ ohms×cm.

EXAMPLE 10

A porous polymer substrate is prepared as follows:

    ______________________________________                                        Naphthalene (#106 200,                                                                           4,150 g                                                      Merck, Darmstadt)                                                             Silica (Syloid 244, Grace) 700 g                                              Stearic acid (#10 0671, 15 g                                                  Merck, Darmstadt)                                                             Antioxidant (Irganox D215, 20 g                                               Ciba Geigy)                                                                   Polyethylene terephthalate, 590 g                                             Merck-Index M, 7546                                                           (#20 025-5, Aldrich)                                                        ______________________________________                                    

The components 2 to 4 are incorporated into molten naphthalene, heatedto about 145° C., and are dispersed by 10 minutes' stirring. Then thepolyethylene terephthalate is introduced with stirring over a period of10 min. The homogeneous mixture obtained is molded into a sheet by meansof a slot die (gap width 200 μm).

The sheet is treated by means of a calender and in the process cooled toroom temperature. The naphthalene is then extracted with toluene. Theporous sheet obtained has a water absorption capacity, according toCobb, of 70 g/m².

The electrically conductive layer is formed as described in Example 1.

To form the dielectric layer, a coating composition is applied whichcomprises:

    ______________________________________                                        Toluene                74 parts by weight                                       Isopropanol  14 parts by weight                                               Poly (vinyl butyral) 7.0 parts by weight                                      (Butvar B-76, Monsanto Chemical Co.)                                          Calcium carbonate (Calcilit 4) 4.4 parts by weight                            Amorphous silicon dioxide 0.2 parts by weight                                 (Syloid Al 1, Grace)                                                          Synthetic amorphous silica 0.4 parts by weight                                (OK 412, Degussa)                                                           ______________________________________                                    

The dielectric layer is applied in an amount of 2 g/m² of the dryconstituents of the coating composition. The dielectric recording layerhas an electrical surface resistivity of 3.2×10⁷ ohms/square and anelectrical volume resistance of 2.8×10⁷ ohms×cm at 50% RH and 20° C.

EXAMPLE 11

Preparation of a porous polymer substrate based on PVC:

    ______________________________________                                        Cyclohexanone      3,950 g                                                      Silica (FK 310, Degussa) 680 g                                                Stearic acid 10 g                                                             Antioxidant (Irganox D215, 12 g                                               Ciba Geigy)                                                                   High molecular weight 610 g                                                   poly (vinyl chloride)                                                         (#34, 676-4, Aldrich)                                                       ______________________________________                                    

The ingredients 2 to 4 are introduced, with 10 minutes' stirring, intothe cyclohexanone heated to about 95° C. and are dispersed. Then the PVCpowder is incorporated by means of stirring. The mixture obtained isformed into a sheet by means of a slot die (gap width 200 μm). The sheetis calendered on a calender and cooled to room temperature.Cyclohexanone is extracted by means of acetone. After drying the poroussheet has a water absorption capacity, according to Cobb, of 85 g/m².

Then the electrically conductive composition is applied as described inExample 1.

The dielectric layer is formed by the following composition beingapplied in a weight of 4 g/m² (after drying):

    ______________________________________                                        Toluene              25 parts by weight                                         Acetone 56 parts by weight                                                    Amorphous sodium/aluminum  3 parts by weight                                  silicate (P 820, Degussa)                                                     Poly (vinyl acetate)/crotonic 16 parts by weight                              acid copolymer (Mowilit CT 5                                                  from Hoechst)                                                               ______________________________________                                    

The dielectric recording layer has a surface resistivity of 2.0×10⁷ohms/square on the one side and 2.5×10⁷ ohms/square on the oppositeside.

The recording materials of Examples 1 to 11 were provided withrecordings in an electrostatic printer CE 300 from Versatec. Areascolored black, cyan, magenta and yellow were formed. Mixed colors wereproduced by mixing of the abovementioned primary colors. The generatedimages had excellent brilliancy. The adhesion of the inks on thedielectric recording layer was good.

We claim:
 1. An electrostatic or electrographic recording compositioncomprising a polymeric base material and an electrically conductivelayer comprising an electrically conductive polymer;said electricallyconductive layer being disposed on at least one surface of the polymericbase material; and a dielectric recording layer having a surfaceresistivity of from 0.3×10⁶ to 3×10⁹ ohms/square disposed on theelectrically conductive layer; said polymeric base material comprising amicroporous synthetic thermoplastic polymer film having a volumefraction of interconnected pores of from >50 vol % to 95 vol %; saidpolymeric base material comprising from 30-90 wt %, based on the totalweight of the polymeric base material, of a finely dispersed organicfiller which is embedded in the polymeric base material; said polymericbase material having a water absorption capacity, determined by means ofthe Cobb value in accordance with ISO 535-1976(E) with a measuring timeof 12 seconds, of from 30 g/m² to 120 g/m² ; said polymeric basematerial having an electrical volume resistance after said electricallyconductive layer is disposed thereon of from 6×10⁶ ohms×cm to 10×10⁹ohms×cm; wherein disposition of the electrically conductive layer on thepolymeric base material results in the polymeric base material becomingimpregnated with the electrically conductive polymer of the electricallyconductive layer.
 2. The recording material of claim 1, whereinthe basematerial contains from 30 wt % to 80 wt %, based on the total weight, offinely dispersed inorganic filler(s).
 3. The recording material of claim1, whereinthe filler contained in the base material comprises calciumcarbonate, kaolin, aluminum oxide, aluminum hydroxide, barium sulfate,precipitated silica or fumed silica or mixtures thereof.
 4. Therecording material of claim 1, whereinthe synthetic polymer of the basematerial is selected from the group consisting of polyolefins,polyesters, polystyrene, polyamide or poly(vinyl chloride).
 5. Therecording material of claim 4, whereinthe synthetic polymer of the basematerial is linear polyethylene or isotactic polypropylene.
 6. Therecording material of claim 1, whereinthe electrically conductive layercomprises sulfonated polystyrenes, copolymers of dimethylammoniumchloride and diacetoneacrylamide, poly(dimethyldialkylammonium chloride)quaternary cellulose acetates, quaternary acrylic resins, copolymers ofdimethyldiallylammonium chloride and N-methyl-acrylamide, poly(vinylbutyral) derivatives or mixtures thereof.
 7. The recording material ofclaim 1, whereinthe dielectric recording layer comprises polystyrene,polycarbonate, polyolefins (which may or may not be halogenated),(meth)acrylic resins, poly(vinyl butyral), polyester resins, polyvinylresins, cellulose acetate, epoxy resins or mixtures thereof.